1. Field of the Invention
The present invention relates generally to a drum-cutter mining machine utilized in longwall mining operations, and, more particularly, to a drum-cutter mining machine which is adaptable for use upon rack structures positioned at either side of a longwall conveyor.
2. Description of the Prior Art
Underground mining operations which involve longwall mining procedures typically utilize electrically powdered drum-cutter mining machines. A drum-cutter mining machine, also referred to as a shearer loader, is positioned proximate to a mine wall, whereat a mineral is sheared from the mine wall face. The drum-cutter mining machine includes at least one, and usually two, circular cutting drums extending from opposite ends of the minimg machine. A first cutting drum, the leading cutting drum, extends at an upwardly projecting angle from the drum-cutter mining machine. The second cutting drum, the trailing cutting drum, extends at a downwardly extending angle from the drum-cutter mining machine. During cutting operations, the leading cutting drum shears a first portion of the mine wall, and the trailing cutting drum shears a second portion of the mine wall. Translation of the mining machine along the mine wall is permitted on a rack structure, or chain, which extends along the face of the mine wall. A drive wheel of the mining machine meshingly engages with the rack to allow translation of the mining machine therealong. One such drum-cutter mining machine is disclosed in West German Patent No. DE-OS 27 32 275. The mining machine disclosed therein contains two drive motors which are positioned to have lengthwise dimensions substantially perpendicular to the lengthwise direction of the rack, and also, therefore, perpendicular to the direction of travel of the mining machine. The drive motors are connected through reduction gears, such as planetary gears, to driving wheels which engage with the rack causing translation of the mining machine therealong. However, the disclosed mining machine may only be driven on a rack which is affixed to the coal face side of a longwall conveyor. The mining machine may not be used in longwall mining operations in which the rack is affixed to the goaf side of the longwall conveyor.
The drive motor utilized by the mining machine may be similar to the asychronous short-circuited rotor electrical motor, steplessly controlled by frequency conversion disclosed in "Longwall Face Machine" Type SEM 235, of Westfalia Lunen.
Also disclosed in the prior art is West Germany Patent DE-OS 31 09 957 which discloses mining machines which are translated along a mine wall face upon two racks. The racks are situated on opposite sides of the longwall conveyor, and drive wheels of the mining machine engage with the respective racks.
Because of the differing positions of rack structures (i.e., positioned on either the coal-face side, or the goaf side of the longwall conveyor), the mining machines heretofore constructed have been designed for use on a specific rack arrangement. The use of a drum-cutter mining machine, once constructed, in conjunction with a different type of rack structure is not possible, or if possible, is only made so after complicated reconstruction of the mining machine.
It is therefore the object of the present invention to provide a drum-cutter mining machine which is adaptable for use with rack structures positioned on either, or both, sides of a longwall conveyor.